Articles of footwear can include an upper, a midsole, and an outsole. The upper can include layers or sections of material that wrap about a substantial portion of the superior, anterior, posterior, medial and lateral portions of the wearer's foot. The upper can also include laces, straps, or the like for securing the footwear to the wearer's foot. The outsole can be a unitary piece of relatively high-friction material that provides traction for the footwear. Also, the midsole can include foam that is disposed between the outsole and the upper for providing cushioned support for the wearer.
In some cases, footwear can additionally include a bladder that contains a fluid, such as a gas or gel. The bladder can be embedded within the midsole, and weight of the wearer and other loading on the bladder can cause the fluid to displace within the bladder. As such, the bladder can resiliently deform and conform to the wearer's foot in order to provide better support and comfort than some midsoles made entirely out of foam. Also, some bladders can be included within the upper, and the bladder can help the upper to fit more snugly against the wearer's foot for greater comfort. These bladders within the upper can also provide a degree of cushioning for the wearer.
Although conventional footwear with bladders have been adequate for their intended purposes, they do suffer from certain disadvantages. Bladders that extend through only a localized portion of the footwear may not sufficiently support the wearer's foot. For instance, the foot may shift laterally within the footwear, and the foot may apply pressure to the footwear at locations that are spaced away from the bladder. As such, the bladder may not provide sufficient support and comfort for the wearer.